Dielectric antenna



Aug. 4, 1953 J. E. EATON 2,648,002 DIELECTRIC ANTENNA Filed Nov. 19,1945 INVENTOR JAMES E. EATON QI LW ATTORNEY Patented Aug. 4, 1953 JainesE- name, Canr'brid e, Mesa, assignor, "bi

mesne assignments, to the states America as represented by the Secretaryof the Navy Applicants November 19, 1945, seriaiNa. 6295671 '5 Claims.(01. zso saesi invention relates to a radio microwave radiation antenna,and more particularly to a dieleetric rod a'ntefn-iahavir'ig 'theaxis ofthe feed section thereof offset from the axis of the dielectric rod ofthe antenna.

object of this invention is to provide a radar antenna which may bemounted directly to a metal surface without destroying the desiredcharacteristics of the radiation pattern produced bythe antenna. I

Another object of this invention is to provide an end-fife antenna foi'radio microwave radiation of novel design which may be mounted directlyupon a metal surface, the design being such as to reduce to a'ininirnumfthe losses due to side lobes normally developed by such antennas.

A pa'rt'ic'iilar object of this inven'tion is to prov i'de an end-fireantenna of the dielectric rod type vv-nichmaybe'mouhtea directly upon ametal surface in which the losses due to side lobes are reduced to aminimum.

A more partieu'lar object or this invention is to provide an end-fireradar antenna of the dielectric rod type having the axis of the feedsection thereof displaced from the longitudinal axis of the rod section.

A still more particular object of this invention is to provide anend-fire radar antenna of the taper rod type having the exciting probethereof displaced from the horizontal axis of the tapered section of therod.

Further objects and advantages of this invention, as well as itsconstruction, arrangement, and operation, will be apparent from thefollowing description and claims in connection with the accompanyingdrawing, in which the figure is a perspective view of an antennaconstructed in accordance with the principles of this invention.

End-fire radio microwave antennas of the dielectric rod type haveheretofore been discovered and are well known in the art. Such antennas,

however, have been subject to various disadvantages in particularinstallations. Such antennas heretofore known in the art have provenunsatisfactory when mounted directly upon a metallic surface such as thewing of an aircraft in that the energy in the main lobe was forced intoside lobes, with a resultant loss of antenna gain. This inventionprovides a novel end-fire antenna in which these undesirable effects arereduced to a minimum.

Referring to the drawing, there is shown a radar antenna constructedaccording to the principles of the invention having a feeding portion'2"] a "tapered radiating portion ii. '1 metallie surface 23, such asthe wing or an an craft, provides a means for mounting the auteam.amehna is 'fdrrne'ddf asolid dielectriaterial such as, for example,polystyrene. An exciting probe 2 is disposed in the feeding section 2 lat rightan'g'le's to theplane which in cludes-the longitudihal axi'strumd g section and the longitudinal-axis of the adia ihgsectibn.exciting probe illu rated as shewaas being the center conductor of aeoaxi'al line-2 5, though any-proper means for exciting thepmtemay be used.It is to be noted that ieed' s'ebfztiori 2| "has the lower portionthereof cut away so as to pro:- vitle a step, the height of the cuteoutstop being represented by the letter h; and "that exciting probe isoriented parallel to inetal surface "23 on which the antenna is mounted.

The following explanation of the'op'eration of the device --isfbelie vedto be acr'iurate, although another .edu-a-lly plausible emanation mayalso be true. In operation, exciting-probe '24 sets a fieldinfeeding-section a l, which act's asa'wave guide to carry energy intotapered section 22. Because of the ofiset relationship of the excitingprobe to the longitudinal axis of the tapered section, the concentrationof the fields developed in the tapered section is greatest in the upperregion thereof. While some energy difiuses into the lower region of thetapered section, this may be reduced to a minimum by properly adjustingthe height h of the step and consequently the displacement of theexciting probe from the axis of the tapered section. In this manner, theside lobes of the antenna pattern can be kept at a minimum value withoutincreasing the beam width in the horizontal plane, and direct mountingof the antenna upon a metal surface is made feasible. In addition tooperating satisfactorily when mounted directly upon a plane flat surfaceas shown in the figure, it has been discovered that the antenna performsequally well when mounted on the fore and aft edge of a metal airfoilsince the presence of the side of the airfoil also fails to cause thepattern of radiation developed by the antenna to deteriorate.

While a particular embodiment of this invention has been disclosed anddescribed, it is to be understood that various modifications and changesmay be made in this invention without departing from the spirit andscope thereof asv set forth in the appended claims.

What is claimed is:

1. An end-fire radar antenna of the dielectric rod type comprising asolid dielectric member having a tapered portion and a rectangularfeeding portion, said feeding portion having an exciting probe insertedtherein, the longitudinal axis of said feeding portion being oflset fromand coplanar with the longitudinal axis of said tapered portion and theaxis of said exciting probe being perpendicular to the plane whichincludes both the longitudinal axis of said feeding portion and thelongitudinal axis of said tapered portion.

2. A radar antenna comprising in combination, a metallic mountingsurface, a. tapered solid dielectric radiating section longitudinallydisposed on said surface, and a rectangular dielectric feeding sectionattached to the larger end of said tapered dielectric radiating section,said rectangular feeding portion having equal width but smaller in crosssection than said radiating section and so disposed with respect to saidtapered section that the longitudinal axis of said feeding section isoffset from the longitudinal axis of said radiating section to establisha spaced relationship between said metallic surface and said feedingsection.

3. A radar antenna comprising, a solid dielectric rod formed into a feedportion and a radiating portion, said radiating portion being uniform inheight and decreasing in width as it extends away from said feedportion, said feed portion being of uniform cross section equal in widthto the large end of said radiating portion but of reduced height at onesurface thereof whereby the longitudinal axis of said feed portion isoffset from the longitudinal axis of said radiating portion.

4. An end fire radar antenna comprising, a solid dielectric rod formedinto a feed portion and a radiating portion, said radiating portionbeing uniform in height and decreasing in width as it extends away fromsaid feed portion, said feed portion being of uniform cross sectionequal in width to the large end of said radiating portion but of reducedheight at one surface thereof, said feed portion being thereby offsetfrom said radiating portion whereby the longitudinal axis of said feedportion is offset from the longitudinal axis of said radiating portion,and an exciting probe disposed within said feed portion and having itslongitudinal axis perpendicular to the longitudinal axis of said feedportion.

5. An end fire radar antenna comprising, a metallic mounting surface, asolid dielectric rod formed into a feed portion and a radiating portion,said radiating portion being uniform in height and decreasing in widthas it extends away from said feed portion, means for attaching saidradiating portion to said mounting surface, said feed portion being ofuniform cross section equal in width to the large end of said radiatingportion but of reduced height abutting said mounting, said feed portionbeing thereby offset from said mounting surface whereby the longitudinalaxis of said feed portion is offset from the longituditudinal axis ofsaid radiating portion, and an exciting probe disposed within said feedportion and having its longitudinal axis perpendicular to thelongitudinal axis of said feed portion, whereby said feed portion whenexcited by said probe acts as a wave guide to carry energy into saidradiating portion with a field concentration greater than in the regionof said radiating portion remote from said mounting surface.

JAMES E. EATON.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,161,292 Hahnemann June 6, 1939 2,369,808 Southworth Feb. 20,1945 2,398,095 Katzin Apr, 9, 1946 2,405,242 Southworth Aug. 6, 19462,415,089 Feldman Feb. 4, 1947 2,419,205 Feldman Apr. 22, 1947 2,425,336Mueller Aug. 12, 1947 2,460,401 Southworth Feb. 1, 1949 2,473,446 RibletJune 14, 1949

